Candide, ou L'optimisme, traduit de l'allemand de M. le docteur Ralph (in English, Candide, or Optimism, translated from the German of Dr. Ralph), written by Voltaire, was first published in 1759. The 1761 edition of the book included revisions made by Voltaire and was titled Candide, or...
Candide, ou L'optimisme, traduit de l'allemand de M. le docteur Ralph (in English, Candide, or Optimism, translated from the German of Dr. Ralph), written by Voltaire, was first published in 1759. The 1761 edition of the book included revisions made by Voltaire and was titled Candide, or Optimism, Translated from the German of Dr. Ralph. With the additions found in the Doctor's pocket when he died at Minden, in the Year of Grace 1759.
Candide is therefore ostensibly narrated by Dr. Ralph, a third-person omniscient narrator who supposedly knows everything about the stories and the characters in the book and who can travel freely through time and in and out of the character's minds. In fact, Dr. Ralph serves only as an intermediary between Voltaire and the persons who told Dr. Ralph the stories, which Voltaire presumably translated from German and put into book form.
Candide is written in a "frame narrative" structure—or a "story-within-a-story" structure—in which Dr. Ralph is telling a story about other stories that were told to him. These individual stories were told to Dr. Ralph by either a first-person or second-person narrator, and the reliability of the narration is entirely dependent on the reliability of the narrator telling the story to Dr. Ralph. Accordingly, the stories in the book might be absolutely true, absolute nonsense, or something in between.
Since Candide is a work of fiction, none of the stories are true. There is no Dr. Ralph, and, as far as we know, Voltaire made up the whole book, all by himself.
For the sake of discussion, however, in order to determine the truth of each story (or part of each story) as well as the reliability of each narrator of each story (or part of each story), it would be necessary to (1) discover the identity of the original narrator of each story (or part of each story), and (2) determine the reliability, or lack thereof, of that narrator based on the information contained in the book about that particular narrator, which information itself might or might not be reliable, depending on the reliability of the narrator who provided the information about original narrator. Second-person narrators of the original stories will be impossible to identify unless they're named in the book or unless Dr. Ralph kept notes and those notes are still available. This is problematic because there is no Dr. Ralph, so there are probably no such notes.
Such an exercise would be utterly futile, of course, and ultimately pointless. Based on the information in the book—which may or may not be reliable—most, if not all, of the characters in the book are lunatics whose reliability is questionable at best.
There's also the question of the quality and trustworthiness of the translation of Dr. Ralph's second-hand and third-hand stories from the original German into French—presumably by Voltaire, although nothing is certain—and then into English, in any of the many, many translations of Candide from French to English which have come down to us in the past 260-odd years.